Surgical procedures often require the application of peripheral nerve blocks, which generally involve injecting a patient with a local anesthetic near a nerve in order to eliminate any pain or sensation during the surgical procedure.
In addition, patients with nerve damage due to maladies such as carpal tunnel syndrome often require the injection of a drug (such as a steroid or an anesthetic) near the nerve. In this respect it should be appreciated that an estimated 40 million Americans suffer from chronic pain symptoms, with more than half of them over the age of fifty-five. And nearly 60% of all of those who suffer from diabetes also have acute peripheral neuropathy. Local anesthesia can be applied to relieve chronic or acute pain situations, with two basic techniques being used: peripheral nerve block and plexus anesthesia. As noted above, peripheral nerve block is the injection of a local anesthetic in the vicinity of a peripheral nerve so as to anesthetize the region surrounding the nerve. Plexus anesthesia is the injection of a local anesthetic in the vicinity of a network of intersecting nerves (i.e., a nerve plexus) in order to anesthetize the entire area of several or all of the nerves stemming from the plexus. Thus, regional nerve blocks and plexus anesthesia can aid patients who suffer from chronic pain such as lower back pain, neck pain, sciatica (from a herniated disc), spinal stenosis and reflex sympathetic dystrophy (a complex regional pain syndrome). In addition, regional nerve blocks and plexus anesthesia can also help those suffering from shingles, cancer and painful peripheral vascular disease.
In order to provide effective peripheral nerve blocks and plexus anesthesia, it is important to first accurately locate the nerves which are to be anesthetized. Peripheral Electrical Nerve Stimulation (PENS) can be used to accurately locate the targeted nerve. In PENS, electrical pulses are sent, via a needle electrode, into the desired nerve(s) so as to trigger depolarization of the nerve and elicit a reaction in the muscle which is innervated by the nerve. A constant current source, delivered via the needle electrode, supplies the depolarizing current to the nerve. The amount of charge received by the nerve depends on the distance between the tip of the needle and the nerve: the closer the tip is to the nerve, the greater the reaction of the muscle. Thus, by monitoring muscle reaction, the peripheral nerve can be reliably located. Once the peripheral nerve has been located, one of several anesthetics, in combination with a steroid and/or opioid, can be administered by the physician.
Needle electrodes are also used in connection with botulinum injections. More particularly, nearly three million botulinum injections are administered annually in the United States for cosmetic purposes or for therapeutic purposes (e.g., for treatment of focal dystonia, or for treatment of painful muscle spasms, etc.). The injection of the botulinum toxin is a process that takes ten to thirty minutes. A topical anesthetic is applied to the area in question for numbing purposes, and then small amounts of the botulinum toxin is injected into predetermined areas with an extremely thin needle. Needle electrodes are used to help identify the appropriate areas for the botulinum injections.
Needle electrodes are also used for electromyography (EMG) studies. More particularly, electromyography is a technique for recording and evaluating the physiological properties of muscles, and is widely used to diagnose and determine the underlying causes of most peripheral neuropathies, including carpal tunnel syndrome and radiculopathy. In electromyography, an electromyograph is used to detect the electrical potential between muscle cells while they are active and at rest. To perform intramuscular EMG, a needle electrode is inserted through the skin and into the muscle tissue. A trained medical professional observes the electrical activity while inserting the needle electrode. In intramuscular EMG, three types of signals are generally studied: (i) the electrical activity of the muscle when the needle is inserted, (ii) the electrical activity of the muscle at rest, and (iii) the electrical activity of the muscle when it is consciously contracted by the patient. Abnormal spontaneous activity of the muscle at rest, and abnormal shape, size and/or frequency of the motor unit potential of the contracted muscle, may indicate nerve and/or muscle damage.
Needle electrodes are also used in many other diagnostic and/or treatment systems.
The needle electrodes currently used for near-nerve anesthesia injections, botulinum injections, EMG applications, etc. are so-called “off-the-shelf” products, in the sense that they have a distal end which is specifically configured according to the intended use and a proximal end which can be inserted into any common cable connector so that the needle can be electrically connected to a neurological testing device. These conventional needle electrodes (which are commonly referred to in the industry as simply “needles”) currently have no means for ensuring that the correct type of needle (i.e., an anesthesia needle, a botulinum needle, an EMG needle, etc.) is connected to a neurological testing device, or for ensuring that a needle has not been previously used.
By way of example but not limitation, two needle electrodes (“needles”) currently commercially available are the STIMUPLEX®—a needle manufactured by B. Braun for drug therapy, and the NEUROLINE® concentric needle manufactured by AMBU® for EMG. The Braun STIMUPLEX® needle is a standard, beveled, hypodermic needle electrode which fits into any Deutsches Institut für Normung (DIN) 42802 cable connector. The Braun STIMUPLEX® needle provides a pinpoint electrode and smooth insertion as well as atraumatic puncture of the skin. The AMBU® NEUROLINE® needle is a standard, beveled, concentric needle electrode, with TEFLON insulation for electrical protection, which also fits into any DIN 42802 cable connector. The AMBU® NEUROLINE® needle provides a sharp tip for easy insertion, and an extra-smooth coating for low insertional friction. Thus it will be seen that the Braun STIMUPLEX® needle used for drug therapy differs significantly in construction from the AMBU® NEUROLINE® needle used for EMG. However, both needles fit into any DIN 42802 connector—meaning that the Braun STIMUPLEX® needle might inadvertently be used in an EMG procedure (rather than in the drug therapy procedure for which it was designed), or the AMBU® NEUROLINE® needle might inadvertently be used in a drug therapy procedure (rather than in the EMG procedure for which it was designed), etc. Neither of the foregoing needles, nor any of the other electrophysiological needles currently on the market, provides an effective or practical means for successfully ensuring that the correct needle is used with a given neurological testing device, or for prevention of its re-use.
In addition to the fact that needle constructions differ according to their intended use, there is a further reason why it may be important to be able to properly identify the needle electrode being connected to a neurological testing device. More particularly, it is anticipated that future designs of needles may incorporate special features that may dictate certain operating parameters. By way of example but not limitation, a needle may have a dielectric on the outside of the needle that requires a minimum breakdown voltage. In this situation, as well as many others, it may be important to ensure that the proper needle is being used with a given neurological testing device.
The re-use of medical needles, while not necessarily a major issue in the United States, is a serious problem in lesser-developed countries where medical resources are frequently scarce. The World Health Organization has estimated that at least half of all medical injections in 17 developing countries were administered with re-used needles, significantly contributing to the skyrocketing rate of AIDS and HIV. An effective and fail-safe means of detecting the re-use of needles would be of substantial benefit to the medical community.
There is, therefore, a need in the industry for a simple, cost-effective approach for ensuring that the proper needle electrode is used with a neurological testing device, and for detecting when a needle has been previously used.
For electrophysiological needles, the interconnect used to couple the needle electrode with the neurological testing device is a key component which is present in all systems. This key component provides an opportunity to ensure that the proper needle electrode is being used with a given neurological testing device and that the needle has not been previously used.
It is, therefore, a principal object of the present invention to provide a simple, cost-effective interconnect which can be used to quickly determine the identity of an electrophysiological needle and, optionally, detect when a needle has been previously used.